We developp few years ago a board to command a LCD character display (4x20), NHD-0420DZ-FSW-FBW.It works perfectly.After some researches, I found NHD-0420DZW-AY5, the OLED characters display.In the datasheet we can see that is compatible with LCD display, but, when i replace my LCD display with the OLED display, it doesn't work.

Is it this OLED display 100% compatible to replace LCD display, with no firmware modification ?